Systems and method for a highly integrated, multi-mode tuner

ABSTRACT

A method for adjusting the signal to noise ratio of a receiver comprises measuring the peak power for an RF signal and determining, based on the measured peak power, whether the RF signal power is within a desired operating range. The method further includes adjusting an RF attenuation for the receiver, when it is determined that the RF signal power is not within the desired operating rang. The method further comprises measuring a peak power foe an IF signal, determining based on the measured peak power, whether the IF signal power is within a desired operating range, and adjusting an IF attenuation for the receiver, when it is determined that the IF signal peak power is not within the desired operating range.

BACKGROUND

1. Field of the Invention

The invention relates generally to tuners and more specifically to ahighly integrated tuner that can be configured for multiple modeoperation and that can be highly integrated.

2. Background of the Invention

A key component in any television or set top box is the tuner. The tuneris the component that allows the television or set top box to tune into,or select, different channels. More generally, a tuner is a keycomponent in any type of receiver that is configured to receive multiplechannels. Thus, the tuner is configured to tune in the desired channel,while blocking or filtering signals on unwanted channels. The tuner isoften also configured to filter received signals and block, or attenuateunwanted noise, or interference signals.

Clearly, the performance of the tuner will effect the overallperformance of the television, or set top box. For example, if the tunerdoes not do a good job of blocking, or attenuating unwanted signals, orsignals on unwanted channels, then the television, or set top box willnot have “good reception.” Good reception is a clear productdifferentiator, especially with the advent of high definitiontelevision, which has raised the stakes, and profile with regard toreception quality for video consumer electronics. The tuner is oftenalso one of the most expensive components in a television or set topbox. Accordingly, tuner design is often driven by the need to improveperformance, while reducing the cost. Reduced cost is often tied toreduced size, and increased component integration.

Much has been done in the area of tuner integration and increasedperformance; however, conventional tuners still suffer performance andintegration limitations that effect the size, cost, and capability ofconventional tuners, and therefore the products they ultimately go into.

FIG. 1 is a diagram illustrating a conventional receiver 100. It will beunderstood that a conventional receiver can comprise additionalcomponents beyond those illustrated. Such components are well known,however, and not relevant to the following descriptions and aretherefore omitted for the sake of brevity. Receiver 100 can, forexample, be included in a cable or terrestrial television or set topbox. A receiver 100 is often interfaced directly with an antenna orcable input from which a multi-channel signal is received.

Conventional receivers can be configured to operate in accordance withone of the various digital and analog standards for both cable andterrestrial applications. The applicable standard defines the overallbandwidth of the system, and the channel scheme. In other words, eachsystem is allocated a certain bandwidth. That bandwidth is then dividedinto a certain number of channels. Each channel is then defined bychannel bandwidth and by a carrier frequency, or plurality of carrierfrequencies.

For example, in the standard broadcast terrestrial system channels 2-13are in the VHF band that extends from 54 MHz to 216 MHz and channels14-83 reside in the UHF band that extends from 410 MHz to 890 MHz. TheUHF band and VHF band are in the Radio Frequency (RF) portion of thefrequency spectrum. Each channel in the standard broadcast terrestrialsystem has a 6 MHz bandwidth, i.e., the VHF and UHF bands are dividedinto a plurality of 6 MHz channels. Each channel is then associated withthree carriers: one for video data, one for color data, and one foraudio data. The video carrier is located at 1.25 MHz above the lowerband edge, the color carrier is located 3.58 MHz above the videocarrier, and the audio carrier is located 4.5 MHz above the videocarrier.

A conventional receiver, such as receiver 100, often comprises severalcomponents including a front end tuner 102, a processor 104, as well asseveral other components including, for example, external filters 114and 120. Tuner 102 typically comprises three stages: an RF stage 122,and Intermediate Frequency (IF) stage 124, and a low IF stage 126. RFstage 122 is configured to receive RF signals, e.g., in the VHF and UHFbands, and convert the RF signals to an IF signal for furtherprocessing. Many conventional tuners, such as tuner 102, are configuredto actually up-convert the RF signal to a higher IF in order to reducethe amount of filtering needed at the input to tuner 102. IF section 124can then be configured to convert the IF signal down to a lower IFsignal for further processing by processor 104. Processor 104 can, forexample, be configured to demodulate the low IF signal in order torecover the actual data, e.g., the video, color, and audio data. Inother implementations, the demodulator can be separate from processor104.

In RF section 122, the received signal is first filtered using a bandpass filter 106, which is configured to filter out, or attenuateunwanted signals outside a desired bandwidth, or range of channels. Thefiltered signal is then often passed to a Low Noise Amplifier (LNA) 108.LNA 108 aids in the reception of very low power signals by amplifyingthe low power signal while adding very little noise itself to theamplified signals. The amplified signal is then typically amplifiedagain by an Automatic Gain Control (AGC) amplifier 110. The gain of AGC110 can, for example, be controlled by processor 104. The signal is thenconverted to an IF signal by mixer 112. Mixer 112 is configured tocombine the received RF signal with a Local Oscillator (LO) signal in amanner design to produce the desired IF signal. The LO signal is tunedto the proper frequency based on the desired channel.

The IF signal is then filtered by filter 114 in IF section 124. Filter114 is typically a Surface Acoustic Wave (SAW) filter. While SAW filtersprovide many advantages, their size and construction often preventintegration with other components, e.g., in tuner 102. The filteredsignal is then mixed to a lower IF by mixer 118, which combines the IFsignal with an IF LO signal. The IF LO signal is tuned to the properfrequency based on the desired channel.

The low IF signal is then filtered by filter 120 to remove unwantedimage signals in low IF section 126 and ultimately passed to processor104. Again, filter 120 is often an external SAW filter. The signal isthen amplified by AGC 116.

As mentioned, conventional tuners, such as tuner 102, suffer severallimitations. For example, conventional tuners often have an external SAWfilter in the IF section, or low IF section that is application andstandard specific. In other words, the bandwidth of, e.g., filter 120 isdefined based on the standard that tuner 100 is configured to implement.For example, in the U.S. the TV and digital cable channels are 6 MHzapart so the appropriate SAW filter would be a 6 MHz filter. In theEurope, the TV and digital cable channels are 8 MHz apart so that theappropriate SAW filter is 8 MHz. As a result, a tuner that is designedto work in the U.S., with a 6 MHz SAW filter, will not work as a tunerdesigned to work in Europe and vise versa. As a result, tunermanufacturers have to build different TV tuners depending on the endmarket and cannot build a single off the shelf tuner for use anywhere inthe world.

Additionally, in conventional tuners, the RF and IF AGCs, e.g., AGCs 110and 112 respectively, are used to adjust the power level of the low IFsignal to a fixed value, regardless of the power level for the signal atthe input to the tuner. Conventional tuners use what is called a takeover point algorithm to adjust the RF AGC and IF AGC of the tuner overthe dynamic range of corresponding standard. Although this technique issimple to implement, it lacks flexibility and can often result in lessthan optimum performance under various and different RF environments,especially in terrestrial applications.

For example, the take over point technique assumes a fixed andpredefined RF condition for the tuner and then optimizes the RF and IFAGC settings for this assumed condition. Often, the assumed condition isa worse case condition in order to ensure that the receiver will workunder such a worse case condition. If the tuner experiences a differentRF condition, however, then the assumed conditions will obviously beincorrect. This can actually have an adverse effect on performance,since the AGC settings will not be optimized for the actual conditions.In the case where the assumed condition for the AGCs take over point isa worse case condition, the tuner will actually be experiencing betterconditions most of the time. As a result, a conventional tuner'sperformance will not be optimized under most conditions, making it highlikely that the Signal-to-Noise Ratio (SNR) at the output of the tuneris not what the tuner could deliver if the take over point could havebeen adjusted for the actual conditions. The inability to adjust thetake-over-point in conventional tuners can have a particularly adverseeffect in terrestrial applications where the RF environment varies fromlocation to location and time to time.

SUMMARY

A tuner that includes dynamic adjustment of the IF and RF AGC valuesunder actual operating conditions enables improved SNR and tuneroptimization under a wider range of operating conditions. The tuner isconfigured to measure the SNR during operation and then adjust the IFand RF AGC values in order to optimize the SNR.

In another aspect, the tuner also includes an integrated IF band passfilter, the bandwidth of which can be programmed for differentstandards.

These and other features, aspects, and embodiments of the invention aredescribed below in the section entitled “Detailed Description.”

BRIEF DESCRIPTION OF THE DRAWINGS

Features, aspects, and embodiments of the inventions are described inconjunction with the attached drawings, in which:

FIG. 1 is a diagram illustrating an exemplary conventional tuner;

FIG. 2 is a diagram illustrating an example tuner configured inaccordance with one embodiment;

FIG. 3 is a diagram illustrating example functional block diagram of ananalog and/or digital demodulator comprising a processor that can beincluded in the tuner of FIG. 3 in accordance with one embodiment;

FIG. 4 is a diagram illustrating a more detailed implementation of thetuner of FIG. 2;

FIG. 5 is a flow chart illustrating an example process for optimizingthe performance of the tuner of FIG. 2 in accordance with oneembodiment;

FIG. 6 is a flow chart illustrating an example method for controllingthe gain of AGCs included in the tuner of FIG. 2;

FIG. 7 is a flow chart illustrating an example method for switchingbetween power modes when controlling the gain of AGCs included in thetuner of FIG. 2;

FIG. 8 is a flow chart illustrating an example method for controllingthe gain of AGCs included in the tuner of FIG. 2; and

FIG. 9 is a flow chart illustrating an example method for controllingthe bandwidth of a receiver included in the tuner of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 is a diagram illustrating an example receiver 200 configured inaccordance with the systems and methods described herein. In theembodiments described herein, it will be assumed that receiver 200 ispart of a television or set top box tuner; however, it will be apparentthat receiver 200 can be a receiver designed for other types ofapplications as well. Thus, the embodiment of FIG. 2 and thedescriptions that follow should not be seen as limiting the embodimentherein to a specific application or architecture.

Receiver 200 comprises a tuner 202, external filter 216 and processor204. Signals received by receiver 200 can first be amplified by LNA 206and then by RF AGC 208, which is under the control of processor 204 asdescribed below. The amplified signal is then sent to peak detector 210,the operation of which is also described in more detail below. Afterpeak detector 210, the signal is mixed with an RF LO signal in mixer 212and converter to an IF signal, which can then be filtered via filters214 and 216. The filtered signal can then be amplified by IF AGC 218,under the control of processor 204 as described below. The amplifiedsignal can then be sent to a second peak detector 220.

After peak detector 220, the signal can then be converted to a low IFsignal via mixer 226. In certain embodiments, receiver 202 can comprisean image rejection block 222 that can include mixer 226. The operationof image rejection block 222 will be discussed in more detail below. Thelow IF signal can then be amplified by Variable Gain Amplifier (VGA)230, before being sent to processor 204. As explained below, processor204 can comprise the demodulator need to convert the low IF signal to abaseband signal for further processing by processor 204.

As mentioned, there are essentially three AGC within receiver 200,namely, RF AGC 208, IF AGC 218, and VGA 230. These AGCs can becontrolled, in certain embodiments, via 3-wire control interface fromdigital processor 204. In other embodiments, the AGCs can be controlledvia 2-wire control interface digital processor 204. In such embodiments,IF AGC 218 and VGA 230 can be controlled with the same external controlvoltage. Alternatively, IF AGC 218 or VGA 230 can be fixed to at apredefined value, e.g., with 4 options, depending on whether VGA 230 iscontrolled externally, and vise versa. Or, in another embodiment, bothIF AGC and VGA can be fixed to a predefined value with four options viaan I2C programming line.

Unlike conventional receivers, processor 204 can be configured toimplement a cognitive algorithm designed to optimize the SNR performancefor the actual RF environment being experienced, as opposed to someassumed condition, such as a worse case condition. This can be effectivefor improving performance, particularly in terrestrial applicationswhere the RF environment and the ratio of undesired signals to desiredsignal is often unknown and changes from location to location and/ortime to time. In general, the idea is to optimize the voltage values ofRF AGC 208 and IF AGC 218 without saturating or compressing thefollowing mixers, 212 and/or 226, respectively, so that the SNR at theoutput of receiver 200 is maximized.

It is desirable to adjust the RF and IF AGC voltage values, and as aresult the tuner gain settings, so that the IF output level is at agiven Full Scale (FS) input to the demodulator, regardless of the RFinput level. In conventional tuners using a conventional take over pointalgorithm, when the RF input signals is very close to noise floor of thereceiver, the demodulator adjusts the IF AGC voltage value, whilemaintaining the RF AGC voltage at a constant, predefined value. As theRF input signal level increases, the demodulator continues to adjust theIF AGC until a threshold, or predefined IF AGC voltage, which is oftenreferred to as the RF AGC take over point, is reached. The RF AGC takeover point is typically defined by determining a RF AGC attenuationlevel that ensures receiver front end will not be saturated for a givenRF input level.

Now, by increasing the RF input signal level even more, once the RF AGCtake over point is reached, then the demodulator will start to adjustthe RF AGC voltage, while maintaining a constant IF AGC voltage in orderto achieve the desired IF output level. Thus, the only degree of freedomfor adjusting the output SNR of the tuner is the RF AGC take over point.But as mentioned, this value is typically based on an assumed worse casecondition and result in less than ultimate performance under manyoperating conditions. Thus, the cognitive algorithm implemented inaccordance with the systems and methods described herein can result inbetter optimization over a broader range of operating conditions.

In the embodiment of FIG. 2, receiver 200 is a heterodyne receiver;however, it will be apparent that the systems and methods describedherein can apply to receivers and/or tuners that are heterodyne orhomodyne in architecture. As a result, the number of AGCs present aswell as the number and type of receiver stages may vary, but a cognitivealgorithm used to optimize the performance in accordance with thesystems and methods described herein can still be applied. In additionto RF AGC 208 and IF AGC 218, tuner 202 also includes VGA 230. In otherwords, there can essentially be three AGCs under control of processor204 implementing the cognitive algorithm described below. The cognitivealgorithm is designed to control RF AGC such that the SNR is maximized,but while also ensuring that RF mixer 212 is not saturated. Similarly,IF AGC 218 is controlled to also ensure that IF mixer 226 is notsaturated.

FIG. 5 is a flow chart illustrating a high level embodiment of thecognitive algorithm described herein. The process of FIG. 5 can beimplemented under the control of processor 204 in order to ensure SNRoptimization at the output of the tuner/receiver. First, in step 502,the RF signal level can be measured, e.g., the peak power strength ofthe RF signals going into RF mixer 212 can be measured. In step 504, itcan be determined whether the RF signal level is within a desirableoperating range. If it is determined that the RF signal level is outsidethe desirable range in step 504, then the signal level can be adjustedin step 506, e.g., RF AGC 208 can be controlled so as to bring the RFsignal level within the desirable range.

Once the RF signal is within the desirable range, then the IF signallevel can be measured in step 508. For example, the peak power strengthof the IF signal going into IF mixer 226 can be measured, e.g., via peakdetector 220. In step 510, it can be determined whether the IF signallevel is within a desirable operating range. If it is determined thatthe IF signal level is outside the desirable range in step 510, then thesignal level can be adjusted in step 512, e.g., IF AGC 218 can becontrolled so as to bring the IF signal level within the desirablerange. Once the IF signal level is within the desirable range, then theIF output can be measure in step 514 and determination can be made instep 518 as to whether the IF output is at Full Scale. If it is not atfull scale, then in step 516 the IF output can be adjusted, e.g., via IFVGA 230, in order to bring it to full scale.

In this manner, the mixers are not saturated but are operating withsignals that are close to the highest level of signals that they cantolerate without distortion. As a result, the mixers should be at theiroptimum SNR performance settings, i.e., when optimum third orderintercept point (IIP3) and Noise Figure (NF) are achievedsimultaneously.

In the example of FIG. 2, peak detectors 210 and 220 are used todetermine the peak power strength of signals going into the mixers. Thishas the advantage that now AGC adjustment can be based on operatingconditions rather than some assumed, e.g., worse case scenario. Incertain embodiments, RF peak detector 210 is a broadband and IF peakdetector 220 can be as wide as the external SAW bandpass filter. Forexample, in one specific implementation, peak detectors 210 and 220 are135 and 3-channels wide, respectively. In such instances, it will not beknown whether the measured power is due to the desired signal alone or acombination of desired and undesired, e.g., adjacent channel signals. Asa result, additional data is needed to determine the Undesired toDesired signal ratio (U/D) of the adjacent channels. Furthermore, sinceit is the output SNR that needs to be maximized, it can be preferable tohave a SNR detector after tuner 202 configured to monitor the SNR of thesignal at the output of tuner 202 after each adjustment of the AGCs inorder to ensure the adjustments are having the desired effect.

The SNR detector just described can be included in processor 204, or thedemodulator that follows tuner 202. FIG. 3 is a diagram illustratingfunctional blocks that can be included in a processor 204, ordemodulator circuit, in accordance with one embodiment of the systemsand methods described herein. It will be clear that such a processor ordemodulator will include other blocks not shown here for the sake ofbrevity.

Processor 204, as illustrated in FIG. 3, can comprise anAnalog-to-Digital Converter (ADC) 302, which can be configured toconvert the low IF signal received from receiver 202 into a digitalsignal. The digital signal can then be down converted to a basebanddigital signal, i.e., in embodiments where tuner 202 is configured toproduce a low IF signal, in Digital Down Converter (DDC) 304. The downconverted signal can then be filtered, e.g., via Digital Low Pass Filter(DLPF) 306. Processor 204 can also include a Digital Automatic GainControl (DAGC) 308, the operation of which is described in more detailbelow, and Digital Signal Processing (DSP) block 310, which can includeall other blocks not mentioned here but required for proper demodulationof the input signal. Processor 204 can also include a SNR detector 312configured to sample the SNR of the input signal. Processor 204 can alsocomprise a common sampling clock 314.

In the embodiment of FIG. 2, RF peak detector 210 is after the RF AGC208 and before mixer 212. In addition, an image rejection filter (notshown) can also follow peak detector 210, i.e., an image rejectionfilter can proceed mixer 212. Accordingly, there can be no selectivitybefore RF peak detector 210. In such situations, peak detector 210 willmeasure the peak power level of the broadband signals being received.

In addition, IF peak detector 220 follows IF AGC 218 but proceeds IFMixer 226, and band stop filter 224 included in image rejection block222. IF peak detector 220 also follows filter 216, which can be a narrowband pass filter, such as a SAW filter. In one embodiment, for example,the SAW filter is centered at 1220 MHz and is 3 channels wide. Thus, IFpeak detector 220 measures the peak power level for the three channelscentered at, e.g., 1220 MHz. In other words, peak detector 220 measuresthe power level for one desired channel and N±1 adjacent undesiredchannels.

DAGC 308 can be configured to provide a digital gain to the signalproduced by DDC 304 in order to bring the desired signal to full scale.This digital gain can be equivalent to

$\left( \frac{U}{D} \right)_{N \pm 1}$ratio, since only the residual of the N±1 channels can reach the ADC.Accordingly, the ratio of

$\left( \frac{U}{D} \right)_{N \pm 1}$can be determined from the DAGC 308 whenever the gain is adjusted tobring the desired signal to full scale. The ratio of

$\left( \frac{U}{D} \right)$can then be used as described below.

In one embodiment, power level measurements from peak detectors 210 and220 are used to control RF AGC 208, IF AGC 218, and/or VGA 230. Forexample, the peak detector measurements can be compared to thresholdvalues. Depending on the results of the comparisons, the gain of thevarious AGCs can be adjusted to ensure that the SNR is optimized andthat the mixers are not saturated. In one specific implementation forexample, RF and IF peak detectors, 210 and 212 respectively, have fourthreshold levels. The thresholds can also be divided between two modes:a high power mode and a low power mode. for example, the followingthresholds can be used:

TABLE 1 Binary Assignment RF Peak Detector IF Peak Detector 00 200 mVp100 mVp  01 160 mVp 70 mVp 10  50 mVp 10 mVp 11  40 mVp  7 mVp

These values can be associated with a binary value as illustrated. Thevalues can then be programmed, e.g., via I²C control lines in thedescending voltage order as shown.

FIG. 6 is a flow chart illustrating an example method for controllingthe AGCs of tuner 202 in a high power mode in accordance with oneembodiment of the systems and methods described herein. Severalvariables are used in the example of FIG. 6. These variables include“rf_pd_en,” “rf_pd_level,” “if_pd_en,” “if_pd_level,” “and“if_out_level.” The variable rf_pd_en can be used to enable the RF peakdetector 210. Similarly, the variable if_pd_en can be used to enable IFpeak detector 220. The variables rf_pd_level and if_pd_level can be usedto store values associated wit the levels determined using RF and IFpeak detectors 210 and 220, respectively. The variable if_out_level canbe used to store a value associated with the output of VGA 230.

With this in mind, the process of FIG. 6 can begin in step 602 with thesetting of the variable rf_pd_en. For example, rf_pd_en can be set to“1” in order to enable the reading of RF peak detector 210. In step 604,rf_pd_level can then be set to “00,” and in step 606, the actual RFlevel can be read. The RF level can be associated with binary values,such as “1” and “0.” A “1” can indicate that the actual level is abovethe associated level, e.g., “00,” while a “0” can indicate that theactual level is below the associated level, e.g., “00.” Thus, in step606, if the level is a “1,” then in step 608, the RF attenuation can beincreased, e.g., via control of RF AGC 208. If, on the other hand, thelevel is a “0” in step 606, then the variable rf_pd_level can be set tothe next level, e.g., “01.”

The actual RF level can then be read in step 612. This time, if thelevel is a “0,” then the RF attenuation can be decreased in step 614. Ifon the other hand, the RF level is a “1,” then if_pd_en can be set,e.g., to “1” in step 616, and if_(—pd)_level can be set to “00” in step618. The IF level can then be read in step 620. If the IF level is a “1”as determined in step 620, then the IF attenuation can be increased instep 622, e.g., via control of the IF AGC 202. If the IF level is a “0,”then if_pd_level can be set to “01” in step 624 and the RF level can beread again in step 626. If the RF level is a “0,” then the RFattenuation can be decreased in step 628. If the RF level is a “1” asdetermined in step 626, then the IF output level can be read in step630. If the IF output level is Full Scale (FS), then the process canend. If the IF output level is not FS, then the control voltage for VGA230 can be decreased in step 632.

As mentioned above, a receiver/tuner configured to operate in accordancewith the systems and methods described herein can be configured tooperate in several power modes, where each mode has its own associatedthresholds for operation and control of the AGCs. For example, in theembodiment described in relation to table 1, the tuner can have twomodes of operation: a high power mode and a low power mode. The flowchart of FIG. 6 is illustrates example operation in a high power mode.FIG. 7 is a flow chart illustrating an example method for switching fromhigh power mode to low power mode in accordance with one embodiment ofthe systems and methods described herein.

The high power mode can be when fully loaded input RF spectrum areexpected to be handled by the tuner. The low power mode can be when thetuner is expected to handle weak, desired signals only. In certainembodiments, the switch between power modes can be allowed during thechannel change. In order to switch to the low power mode, the tunerneeds to ensure that input signal is “weak” and “desired” only. Theweakness, or strength of the signal, can be measured, in step 702, by RFand IF peak detectors 210 and 212, respectively. In step 704, if it isdetermined that the measured signal power is below the “10” value, thenthe signal can be considered weak; however, the measured signal powermay not be due entirely to the desired signal. In other words, some partof the measured signal power can be due to undesired signals.

After the digital low pass filtering by DLPF 306, DAGC 308 can beconfigured to adjust the digital gain to ensure the signal level is atfull scale. The digital gain from DAGC 308 can be directly proportionalto voltage ratio

$\left( \frac{U}{D} \right)_{N \pm 1}.$Thus, the ratio

$\left( \frac{U}{D} \right)_{N \pm 1}$can be determined in step 706, from DAGC 308.

Thus, if it is determined in step 706 that

${\left( \frac{U}{D} \right)_{N \pm 1} \prec {0\mspace{14mu}{dB}}},$then it can be determined in step 706 that there is no undesired signalcomponent in the signal. Under this determined condition, the tuner canthen be switched, in step 708 to the low power mode.

If it is determined in step 700 that

${\left( \frac{U}{D} \right)_{N \pm 1} = {0\mspace{14mu}{dB}}},$then it can be determined in step 710 that the input signal into thetuner is equally due to signals on the adjacent channels and to signalson the desired channel. Under this determined condition, the tuner canthen be switched, in step 708 to the low power mode.

If it is determined in step 712 that

${\left( \frac{U}{D} \right)_{N \pm 1} \succ {0\mspace{14mu}{dB}}},$then it can be determined in step 712 that the input signal into thetuner is mostly due to signals on the adjacent channels and not to thedesired channel. Under this determined condition, the tuner can, in step714, be controlled to remain in high power mode.

FIG. 8 is a flow chart illustrating an example method for controllingthe AGCs of tuner 202 in a low power mode in accordance with oneembodiment of the systems and methods described herein. First, in orderto adjust the AGCs, processor 204 can be configured to look, in step802, at the measurement supplied by RF peak detector 210. If themeasurement is below the value associated with “10” but above the “11”value, as determined in steps 804 and 808, then processor 204 can beconfigure to simply maintain the RF attenuation level as is. If themeasurement from RF peak detector 208 is determined, in step 804, to beabove the “10” value, however, then processor 204 can be configured toadjust RF AGC 208 so as to increase the RF attenuation in order to bringthe measured power back between the “10” and “11” values, in step 806.If it is determined in step 808 that the measured RF power is below the“11” value, then processor 204 can be configured to control RF AGC 208in order to reduce the RF attenuation and bring the measured power backbetween the “10” and “11” values, in step 810.

In step 812, processor 204 can be configured to check the measurementsupplied by IF peak detector 220. If the measurement is below the “10”value, but above the“11” value, as determined in steps 814 and 818, thenprocessor 204 can be configured to simply maintain the IF attenuation.But if it is determined in step 814, that the measure power is above the“10” value, then processor 204 can be configured to control IF AGC 218,in step 816, in order to bring the measured value back between the “10”and “11” values. If it is determined in step 818 that the measured poweris below the “11” value, then processor 204 can be configured to controlIF AGC 218, in step 820, in order to bring the measured value backbetween the “10” and “11” values.

Processor 204 can be configured to adjust VGA 230, in step 824, so thatthe signal at the output of tuner 202 is full scale after eachadjustment of the AGCs as determined in step 822. Additionally, incertain embodiments, SNR detector 312 can be monitored before and afterany changes in AGC settings to make sure that the desired result isobtained.

As mentioned, tuner 202 can comprise an image rejection block 222. Imagerejection block can comprise a bandstop filter 224, IF mixer 226, a bandstop filter 227, and band pass filter 228. Filters 224, 227, and 228taken together behave as an equivalent bandpass filter with programmablebandwidth. For example, in one embodiment, the bandwidth of theequivalent bandpass filter included in image rejection block 222 can becontrolled directly by processor 204. In other embodiments, a separatecontroller can be included to control the bandwidth of image rejectionblock 222. For example, in one implementation, bandpass filter 228include I²C control inputs in order to receive bandwidth controlsignals.

Providing controllable bandwidth via image rejection block 222 canimprove tuner performance and allow for a global tuner design that canoperate in multiple modes, i.e., operate in accordance with multiplestandards. As mentioned above, a receiver 200 can be configured tooperate in both digital and analog systems as well as both cable andterrestrial systems. Accordingly, tuner 200 can, for example, beconfigured to implement the following standards: DOCSIS, Euro-DOCSIS,DVB-C, DVB-T, ATSC, NTSC, PAL, and SECAM. Often these standards specifydifferent channel bandwidths, which requires the tuner designer todesign standard specific tuners. By incorporating programmablebandwidth, e.g., via image rejection block 222, the designer can nowdesign a single global tuner. Further, the external filter 120, found inconventional tuners, can be eliminated, which reduces the number ofcomponents and, therefore, can help reduce the size and costrequirements associated with conventional tuners.

In addition, the bandwidth programmability provided by image rejectionblock 222 can be used to further optimize SNR. For example, the SNR canbe monitored using SNR detector 312, and the bandwidth of imagerejection block 222 can be adjusted based on this measurement. FIG. 9 isa diagram illustrating an example method for controlling the bandwidthof tuner 202 in accordance with one embodiment of the systems andmethods described herein. First, in step 902, the SNR can be determined.If the SNR is deficient, then is can be determined whether the poor SNRis due to adjacent channel interference in step 904. If there isadjacent channel interference, then the linearity of tuner 202 will beeffected, causing the poor SNR. In this case, the bandwidth of receiver202 can be narrowed, in step 910, e.g., via control of image rejectionblock 222, in order to block the adjacent channels.

In step 912, it can be determined if the SNR is improved. If it hasimproved, then the process can end. If not, then the bandwidth can bewidened in step 906.

If it is determined in step 904 that adjacent channels are not effectingthe SNR, then it can be determined, in step 906, whether the poor SNR isdue to group delay distortion. If the poor SNR is due to group delaydistortion, then the bandwidth of receiver 202 can be widened in step908 to remove the group delay distortion. In step 910, it can bedetermined if the SNR is improved. If it has improved, then the processcan end. If not, then the bandwidth can be narrowed in step 908.

It should also be pointed out that in certain embodiments, receiver 202can comprise a relatively wide bandwidth on chip filter 214, whichallows for the use of a relatively narrow band filter 216, e.g., anarrow band SAW filter, external to receiver 202.

FIG. 4 is a more detailed diagram of a receiver 400 configured inaccordance with the systems and methods described herein. As can beseen, receiver 400 comprises a RF input (RF In) on which receiver 400receives an RF input signal. The RF signal is then amplified via LNA402, before being passed to RF AGC 404, which is followed by RF peakdetector 406. As can be seen, receiver 400 uses differential signals,but it will be clear that the systems and methods described herein canbe implemented with single ended or differential signals.

After peak detector 404, the signal is filtered by image filter 408 andconverted to an IF signal by mixer 410. The IF signal is then filteredby on chip filter 412 and then off chip filter 414. As mentioned, onchip filter 412 can comprise a relatively wide bandwidth, while off chipfilter 414 can comprise a relatively narrow bandwidth.

The filtered IF signal can then be passed to IF AGC 416, and then IFpeak detector 418. IF peak detector 418 can be followed by a buffer, ora fixed gain amplifier, 420. The signal can then be passed to an imagerejection block 456. Image rejection block 456 can comprise a quadraturemixer 424 configured to convert the IF signal to a low IF signal. Imagerejection block 456 can also comprise a first poly phase filter 422 anda second poly phase filter 426, as well as programmable filter 430. Apair of VGAs 434 and 436 can follow image rejection block 456 at theoutput of the tuner portion of receiver 400.

Receiver 400 can comprise a IF AGC control circuit 438 configured toreceive control signals from a processor, or controller that can then beused to control the attenuation/gain in the IF section of tuner 400.Receiver 400 can also comprise an input (RF Att) that can be configuredto receive control signals for controlling the attenuation of RF AGC404. Receiver 400 can also comprise a IF filter tuning circuit 440configured to control the band width of image rejection block 456.

Two synthesizers 448 and 444 can be included in receiver 400 andconfigured to generate the relevant RF and IF Lo signals used by mixers410 and 424. Synthesizer tuning circuit 446 can be included andconfigured to tune synthesizers 448 and 444 for the appropriate channel.

It should also be pointed out that tuner 400 can include an integrateU/C block. The U/C block can be configured in the case of multi-tunerapplications. For example, when the cable TV signal is split into three,first for TV, second for VCR, and third for cable modem. Then, by havingan external LNA and bypassing the internal LNA, 402, via U/C block,multiple tuner can be configured. In conventional tuners, the U/C bockis external to tuner 400. Integrating U/C block 458 within tuner 400 canreduce size and cost requirements.

While certain embodiments of the inventions have been described above,it will be understood that the embodiments described are by way ofexample only. Accordingly, the inventions should not be limited based onthe described embodiments. Rather, the scope of the inventions describedherein should only be limited in light of the claims that follow whentaken in conjunction with the above description and accompanyingdrawings.

1. A method for adjusting the signal to noise ratio of a receiver,comprising: measuring the peak power for an RF signal; determining,based on the measured peak power, whether the RF signal power is withina desired operating range; adjusting an RF attenuation for the receiver,when it is determined that the RF signal power is not within the desiredoperating range; measuring a peak power for an IF signal; determiningbased on the measured peak power, whether the IF signal power is withina desired operating range; and adjusting an IF attenuation for thereceiver, when it is determined that the IF signal peak power is notwithin the desired operating range.
 2. The method of claim 1, whereindetermining whether the RF signal power is within a desired operatingrange comprises determining, based on the measured peak power, whetherthe RF signal power is above a threshold, and reducing the RFattenuation of the RF signal power is above the threshold.
 3. The methodof claim 1, wherein determining whether the RF signal power is within adesired operating range comprises determining, based on the measuredpeak power, whether the RF signal power is below a threshold, andincreasing the RF attenuation of the RF signal power is below thethreshold.
 4. The method of claim 1, wherein determining whether the IFsignal power is within a desired operating range comprises determining,based on the measured peak power, whether the IF signal power is above athreshold, and reducing the IF attenuation of the IF signal power isabove the threshold.
 5. The method of claim 1, wherein determiningwhether the IF signal power is within a desired operating rangecomprises determining, based on the measured peak power, whether the IFsignal power is below a threshold, and increasing the IF attenuation ofthe IF signal power is below the threshold.
 6. The method of claim 1,further comprising adjusting the signal gain at the output of thereceiver to ensure that the output is at full scale, whenever the RF orIF attenuation is adjusted.
 7. The method of claim 1, further comprisingdetermining whether the receiver is in a high power mode or a lowerpower mode, and adjusting thresholds used to determine whether the RFand IF signal powers are within a desired operating range, based on thedetermination of whether the receiver is in a high power or low powermode.
 8. The method of claim 7, wherein determining whether the receiveris in high power mode or low power mode comprises measuring a peaksignal power and comparing the measured peak signal power to athreshold.
 9. The method of claim 8, wherein determining whether thereceiver is in high power mode or low power mode further comprisesdetermining the U/D ratio and determining the receiver is in low powermode if the determined U/D is less than or equal to 0 dB.
 10. The methodof claim 1, wherein determining whether the RF signal power is within adesired operating range comprises determining whether an RF mixer is insaturation, and wherein adjusting an RF attenuation for the receiver,when it is determined that the RF signal peak power is not within thedesired operating range comprises lowering the RF attenuation when it isdetermined that the RF mixer is not saturated or well bellowcompression.
 11. The method of claim 1, wherein determining whether theIF signal power is within a desired operating range comprisesdetermining whether an IF mixer is in saturation, and wherein adjustingan IF attenuation for the receiver, when it is determined that the IFsignal peak power is not within the desired operating range compriseslowering the IF attenuation when it is determined that the IF mixer isnot saturated or well bellow compression.
 12. A receiver including atuner and a processor coupled with the receiver, the tuner comprising: aRF section, the RF section including a RF AGC and a RF peak detector;and an IF section, the IF section comprising an IF AGC and an IF peakdetector, the processor configured to: determine, using the RF peakdetector, whether an RF signal power for the RF section is within adesired operating range; adjust the RF AGC in order to adjust the RFattenuation for the receiver, when it is determined that the RF signalpower is not within the desired operating range; determine, using IFpeak detector, whether an IF signal power for the IF section is within adesired operating range; and adjust the IF AGC in order to adjust the IFattenuation for the receiver, when it is determined that the IF signalpeak power is not within the desired operating range.
 13. The receiverof claim 12, wherein the processor is configured to determine, based onthe measured peak power, whether the RF signal power is above athreshold, and adjust the RF AGC in order to reduce the RF attenuationof the RF signal power is above the threshold.
 14. The receiver of claim12, wherein the processors configured to determine, based on themeasured peak power, whether the RF signal power is below a threshold,and adjust the RF AGC in order to increase the RF attenuation of the RFsignal power is below the threshold.
 15. The receiver of claim 12,wherein the processor is configured to determine, based on the measuredpeak power, whether the IF signal power is above a threshold, and adjustthe IF AGC in order to reduce the IF attenuation of the IF signal poweris above the threshold.
 16. The receiver of claim 12, wherein theprocessor is configured to determine, based on the measured peak power,whether the IF signal power is below a threshold, and adjust the IF AGCin order to increase the IF attenuation of the IF signal power is belowthe threshold.
 17. The receiver of claim 12, further comprising avariable gain amplifier, and wherein the processor is further configuredto adjust the gain of the variable gain amplifier in order to adjust thesignal gain at the output of the receiver to ensure that the output isat full scale, whenever the RF and/or IF attenuation is adjusted. 18.The receiver of claim 12, wherein the processor is further configured todetermine whether the tuner is in a high power mode or a lower powermode, and adjust thresholds used to determine whether the RF and IFsignal powers are within a desired operating range, based on thedetermination of whether the tuner is in a high power or low power mode.19. The receiver of claim 18, wherein determining whether the tuner isin high power mode or low power mode comprises measuring a peak signalpower using the RF peak detector and/or the IF peak detector andcomparing the measured peak signal power to a threshold.
 20. Thereceiver of claim 19, wherein determining whether the receiver is inhigh power mode or low power mode further comprises determining the U/Dratio and determining the tuner is in low power mode if the determinedU/D is less than or equal to 0 dB.